/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.client;

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Most simple HostProvider, resolves only on instantiation.
 * 
 */
public final class StaticHostProvider implements HostProvider {
	private static final Logger LOG = LoggerFactory.getLogger(StaticHostProvider.class);

	private int currentIndex = -1;

	private int lastIndex = -1;

	private final List<InetSocketAddress> serverAddresses = new ArrayList<InetSocketAddress>(5);

	/**
	 * Constructs a SimpleHostSet.
	 * 
	 * @param serverAddresses possibly unresolved ZooKeeper server addresses
	 * @throws UnknownHostException
	 * @throws IllegalArgumentException if serverAddresses is empty or resolves to
	 *                                  an empty list
	 */
	public StaticHostProvider(Collection<InetSocketAddress> serverAddresses) throws UnknownHostException {
		for (InetSocketAddress address : serverAddresses) {
			InetAddress resolvedAddresses[] = InetAddress.getAllByName(address.getHostName());
			for (InetAddress resolvedAddress : resolvedAddresses) {
				this.serverAddresses.add(new InetSocketAddress(resolvedAddress.getHostAddress(), address.getPort()));
			}
		}

		if (this.serverAddresses.isEmpty()) {
			throw new IllegalArgumentException("A HostProvider may not be empty!");
		}
		Collections.shuffle(this.serverAddresses);
	}

	public InetSocketAddress next(long spinDelay) {
		++currentIndex;
		if (currentIndex == serverAddresses.size()) {
			currentIndex = 0;
		}
		if (currentIndex == lastIndex && spinDelay > 0) {
			try {
				Thread.sleep(spinDelay);
			} catch (InterruptedException e) {
				LOG.warn("Unexpected exception", e);
			}
		} else if (lastIndex == -1) {
			// We don't want to sleep on the first ever connect attempt.
			lastIndex = 0;
		}

		return serverAddresses.get(currentIndex);
	}

	public void onConnected() {
		lastIndex = currentIndex;
	}

	public int size() {
		return serverAddresses.size();
	}
}
